Aircraft having rotating blades or wings



Dec. 19, 1944. REwrr 2,365,357

AIRCRAFT HAVING ROTATING BLADES OR WINGS Filed Dec 18, 1940 3 Sheets-Sheet l I r INVENTOR: 83 R 1d flfl'czazll S PATENT ATTORNEY 1944- R; H. PREWITT AIRCRAFT HAVING ROTATING BLADES OR WINGS Filed Dec. 18, 1940 5 Sheets-Sheet 2 Dec. 19, 1944. R. H. PREWITT 2,365,357

AIRCRAFT HAVING ROTATING BLADES OR WINGS Filed Dec. 18, 1940 5 Sheds-Sheet 3 INVENTOR- 68 66 R d HPreau'ff 72 25 BY 741, (4M.

PATENT ATTORNEY Patented nee. 19, 1944 Richard H. Prewitt, Lansdowne. Pa., assignor to Kellett Aircraft Corporation, a corporation of Delaware Application December l8; 1940, Serial No. 370,572

. 6 Claims. (Cl. 244-17) The present invention relates to aircraft and more particularly to improvements in the mounting of the blades of propellersand rotor systems same. This invention is further concerned with improvements in the vmounting details of the blades and their construction for the purposes of reducing weight and friction and also to automatic interconnections between the blade pitch and drive mechanism controls of rotative wing aircraft of the jump take-oi? type.

One of the major objects of the present invention is the provision of means for controlling the incidence angles of rotating blades of either horizontal or vertical thrust propellers, or the rotating wing systems of autogiros. A further object is the provision of such wings which are operated under conditions of centrifugal tension without involving excessive friction and to further improve such devices by the simplification and elimination of parts heretofore found necessary and to thereby provide structures which are lighter in weight. It is a further object of the invention to provide both manual and automatic means for controlling the pitch angle ofpropell'ers and/orrotor blades while they are in operation. A further object contemplates a novel cable control arrangement for the actuation of the blade pitch changing mechanism. Among the other objects.

and the Jump take-E clutch control whereby the latter is automatically "tripped when the blade and means for adjusting the blade pitch of the Fig. 5 shows the application oi. thedevice to a two-bladed controllable pitch propeller;

Fig. 6 shows an elevation and partial sectional view of the hub and blade mounting assembly illustrating the method of varying the pitch angle of the blade; v

Fig. 7 is a plan view of the mechanism at the hub end of the rotor blade as used for controlling its pitch angle;

Fig. 53 is a sectional view through the pitch angle controlling mechanism taken along the blade stops.

All

pitch is manually adjusted into the high lift position. l Other objects and advantages of the present invention may occur to those skilled in' this art after a reading of the following description and y the accompanying drawings forming a part hereof, in which; I

Fig. 1 shows an elevation of an aircraft of the rotating wing type incorporatinga tractor pro-- peller and rotor system with a portion of the fuselage broken away to show the blade pitchcontrol mechanism;

Fig. 2 is a detail drawing showing the operating lever for'manual and/or automatic control of the blade pitch angles; v

Fig. 3 shows a detail of the automatic, clutch releasing device; v

Fig. 4 shows. an installation of the propeller blade pitch angle control device applied to a threebladed tractor propeller;

Referring to Fig. '1, there is shown an elevational view of an aircraft of the rotating wing type'provided for jump take-ofi, in which the general arrangement-pf the present invention is outlined. The aircraft to is comprised of the rotor system I composed in the present instance of three rota-table blades, mounted upon the hub 2' and supported from the fuselage of the aircraft by the pylon 3. The rotor system I isarranged to be selectively driven through the universal joints l and the drive shaft 5 by the rotor starter 6, and the engine 8, having an engine starter i, the engine also being arranged for the drive of the tractor propeller 9. The aircraft is otherwise provided with the usual landing gear H and tail surfaces l2 conventionally found on this type aircraft.

The tractor propeller is of the contro'llablepitch type, the blade pitch being controlled through the. lugs l3 mounted on each blade and pivotally connected to the links M, the radially extending arms [5 journalled on bearing l6, and theslidable collar l'l, all as more clearly shown in Fig. 5. The

collar 11 is pivotally connected to a link l8 and" the bellcrank l9 .pivotally mounted upon themgine at Illa and having its opposite terminal pivotally connected to thecontrol rod 20 guided by the-bearings 20b and terminating with a control handle 20a in the cockpit of the airplane accessible to the pilot. The clutchfl which has been indicated in the drawing is of the external band type, but may be of any other suitable -construcually operated handle 23 which will be subse-' quently described more Iully.

Referring now to Fig. 2, there is 'shofwn the 'descbed.

arrangement of the handle lever 25 and cable 25 by which the rotor blade pitch angles are oon= trolled; The control lever 23 is attached through a torque shaft ill? to levers 2t and El and suitably iournalled and supported by brackets 35a and 35b from the fittings we on the aircraft structure, being so arranged that when lever 25 is pulled back against the stop 28 the slida-lole plunger 25 is moved forward so that its large circular sec= tion at 3b substantially fills the hole in the tongue 38a in the plunger 35. It should also be noted that when the lever is in the forward position the opposed stop '32 causes the plunger 29 to move back so that 'the small diameter of the plunger shown at 33 permits the plunger 35 to move up so that its upper face 5% comes against the lower edge of the quadrant 35 as shown in dotted lines in Fig. 2. The spring tie in the upper end of the control tubular handle is will tend to keep the plunger 3i against the lguadrant 55 when the control lever 28 moves up and back due to the force of; the spring 3? (Fig. 1) acting on lever 27! through cable fill which runs over pulleys B2. in combination with automatic control means ro= tating in the rotor head'- As the control lever 23 moves back along the quadrant 35 the spring 3th will force the upper edge as of the plunger 3i into notch 38 which represents the pitch angles of the rotor blades l in normal flight. Hand button 53 fixed to the plunger rod 3i provides a means of releasing the lever 25 from its latched position in which the tongue em engages the notch. When the lever is back against the stop 28 the blades are in low pitch and when it is down against the stop 32 the blades are in high pitch.v When lever to is pulled further aft than shown the terminal 39 of lever 26 moves downward about the pivot to of the lovers 2%, 28 and 271 thereby pulling cable 25 downwardly and rearwardly in relation to pivot to. Lever 28 is slotted in its upper section at 26c and pivot shaft to is recessed at 48c directly under cable 25, such that when the point 39 is lowered sumciently so that the line of cable 25 reenest shown at 8. with the propeller shaft at 38 carrying eithertwo or three radially extending stub arms 59 (Fig. 4 indicates a three bladed pro= passes below the pivot to. the tension in cable.

ing block a. carried by the airplane structure, both levers being displaced laterally as indicated by cable 8| passing lever 23 on the near side of the reader, therefore, levers 22 and 23 move together'about pivot 44 transmitting the engaging load to push-pull rod 41. formed into two open end lips Ii-straddling the cable 4| on which there islocated a fixed stop 45.

The purpose of the stop is to automatically dis-l engage the rotorclutch 2! when the pitch control lever 2l'is moved from low pitch to high pitch thereby preventing the possibility of alj'ump takeoff with the rotor clutch engaged. It will be noted that the fixed stop 15 on cable II is conical in shape and that an internal portion 46a of the "fork lips on lever 22 is sloped. The purpose of this arrangement is to permit'conical stop to move upward and to the right through forlc arm 48 of lever 22 without creating any appreciable force on theend oflever 22. However, when stop 45 is moved downward in the opposite direction it engage Referring to Fig. 4, the nose of the engine is the fork end of lever; 22 as The lower end of 22 is a peller and a two-=bladed system is shown in Fig. 5). The radial stub arms fit are machined cylindrically at 59 upon which are mounted bearings ateither end ofv the shaft stub. A circle of lugs 52 surround the radial arms :39 in a manner shown at the opposite blade at the bottom of the figure. The shank of the propeller. is provided with the same type lugs also indicated at 52 and illustrated in greater detail in Figs. 9 and 10. In addition, the shank of the propeller a carries a machined shaft 53 which fits over bearings 5i located on shafts 56. Tension=torsion rods or links 56 are concentrically arranged about the centre shaft in the same manner as shown in Fig. 8 for the rotor and are hooked ovr the lug projections 52 in the manner shown in Figs. 9 and 10. The control arm M is pivotally connected'to the far side of the shank of the propeller blade 9 through a' pivot 50 and a control post 53 which is rigidly fixed to the shank of the propeller blade at a point outboard of the fittings 52. When pushrod i8 is moved co-axially with the propeller shaft it causes collar I l to slide in and out along the propeller shaft 68. This motion is transmitted through a bearing (not shown in this figure but illustrated at is in Fig. 5) to lever l5 which in turn causes the links M to move fore and aft substantially co-axially with the propeller shaft. This motion causes a rotation of the propeller blade 9 about the hub shank 48 and shaft portion 59.

The two-bladed propeller arrangement illustrated in Fig. 5 utilizes a. slightly different construction than the three-bladed system shown in .Fig. 4. It will be noted that the arrangement noted in Fig. 4 is equally applicable to propellers having any number of blades. gine nose section is also. shown at 8]. The elongated propeller shaft 48 carries a fork yoke member 55 in which are mounted the shanks of the propeller blades 9 at 56 using any suitable bearing between yoke 55 and propeller blade s. as for example, abronze bearing, illustrated at 57. It will be noted that the machined shaft portions of the propeller shank ends shown at 55 and 59 are mutually joumalled within the bearings 5B which are located at the ends of the over-lapped or telescoped shank ends, thus providing adequate rigidity to assist in taking the bending moments of the propeller blades. The arrangement of the plurality of lugs 52 and the corresponding rods. to

are similar to those'shown m Fig. 4 and in detail in Figs. 8, 9 and 10. Thus it will be seen that the blades 9 are free to rotate in the bearings 51 at I shank position 56 and that when the blades are rotated in- O posite directions the machined shank shaft 58 rotates in relation to machined v shank shaft 59 on the interposed bearings 50. The lugs and shaft portions are housed in a suitable fairing 122 for protection and reduction in drag.

It will be further seen that when the blades s lare rotated in opposite directions, the lugs on the.

' right hand shaft shown at 52 will be rotating in relbtion fo the corresponding lugs 52 shown on the left hand propeller shank. This relative ro- 'm tation causes-the link 'members 54 to rock about 1| blades, tending to them remain at a given I the lug 52 and to have a slope in relation to the centre line passing through the centre of shank members 56 .of blades 9. This slope on. the link members 54 causes 9. self-centering between the In Fig. 5 the enseases 3 pitch angle. The control mechanism shown in Fig. 5 is also similar to the mechanism shown in Fig. i. For instance, the control posts l3 are fixed to the propeller blades 9 near their shanks and the pivots or on the corresponding sides of a the shanks such that fore and aft motion of the connecting link it causes the blades 9 to turn in their respective pivots 5b. The motion of the control link it is controlled through the push- 1 pull members it and 20, through the lever' it ill pivoted at its, collar ll, bearing i6 and control arms i in a manner as described above. I

Fig. 6 shows an assembly elevation of a cut away section of therotor hub ii, the extension link ti, rotor blade fork 62, and the blade. pitch change operating mechanism, a clarification of this figure being shown also in the plan view of Fig. 7. Hub case 2 carries a cap arm it attached to its upper end'in which are mounted radial bearing a l and thrust bearing 65. At the lower 2Q) end of hub case 2 is an inserted end plate 66* which carries bearing 8'? and fixed sheath portion oi the Bowden cable 25. The hub shaft db rotates in bearings b t, to arid ti. The bearings and ta are clamped inplace through collar lb which is threaded on tothe rotatable hub shaft bit, the main lift loads being taken through this collar into hub cap $3. The beveled gear ii is splined to hub shaft to, and clamping nut l2,\

which is threaded to shaft 6%, maintains gear ll 31' end. The hub end of cable as is fixed in. swaged. 35

end it which is in turn screwed into member 71 3. Member it carries a projectinglug at it which moves in a parallel slot dirt in stand pipe 32, thus the assembly oi members "it and it and cable 25 are tired so that they cannot rotate in relation so to the ,hub case 2. Between member it and rod iii, bearing to is inserted Nut ti at the lower end of rod it anchors the, latter to the inner portion of bearing it. Just above bearing it rod to is expanded into a disc to to which are as attached swaged ends it at the end of cables at, only one of which is shown. in order to cause rod it; to rotate with hub shaft to, rod id is tri angularly shaped in cross 'section. Guide plate which rotates with hub shait do likewise has a triangulai'ly shaped opening to fit rod iii. By this mating of the two irregular parts, that is section of rod i9 and plate Fit, the assembly above bearing it rotateswith the hub shaft bit. In

modifications where it might be desirable to assist to pivoted at tilt and till, a parallelogram linkage the cable to in drawing the assembly downwardly within the standpipertfi to :0; so. the desired tension in cable ii i, a tension spring is preferably attached between the member it and the bottom plate odor tbs. Extension links iii are attached to'liub shaft through pivot to carrying a droop stop do and caning stop On the top of hub shaft bit are mounted brackets supportingpulley hous fit which is rockable about pivot til, pulley iii beor the mounted within the .rockable pulley bracket (it. The rcckable position of pulley housing or tit. attached to extension arm iii through clamp structure M will cause pulley guard at to rotate about pivot tt carrying pulley ti along with the guard thereby changim the length of cable to to shortened. From a study of Figs. 6 and '7 it may Y of this cable which would occur if this compen eating device were not incorporated. Pulleys and 9b are also fixedly attached to clamp til leading cable-lit out to the blade incidence angle control mechanism without being substantially afiected by changes in the coning angle of the blade. Blade fork arm 62 is attached to extension link ti through vertical hinge Bl. A suitable internal self-centering damper is provided, operating on centering cam 93 and limiteclin. its mo-' tion by the disappearing stop it, having its inner telescoping part bearing against lug tile and the interposed spring tbs as shown in detail in Fig. 11. The tapered pin to engaging the portion die of the fork arm limits the movement of the latter but when it'is desired to fold the blades together the pin is merely pushed in against the'spring and rotating the same a quarter -turnwith a screw=driver, whereby it is locked in its retracted position.

A self-aligning bearing tilt is fitted over the outboard stub end 62a of the fork or and within the blade shank itl. The lugs 52 and tensiontorsion rods lit are similar to those described previously, as shown in Figs. d and 5, and to be subsequently described in connection with Figures o, 9 and 10, in that they carry the centrifugal loads between the blade member lot and the blade fork (it. In flight the rubbing faces 3 92 between members t2 and iti, are held apart due to the centriiugai load in the blade i In this conditionoi operation, bearing lilo transmits only the shear load resulting iroin whatever bending there may be in members 62 and tilt. When the machine is.

sirable to incorporate shims at these suriacesior the purpose of adjustment and control oi wear. it may be seen that the blade will be held in cantilever position when stop to on extension -link iii droops orrotams downwardly-against mating section hub [39.

it better visualisation of the arrangement and operation of spring toil and controlling levers too, 1

its and Mo can beobtained by a study of Figure which is a plan view of the blade root section shown in Figure 6. The pitchcontrol levers tilt) and Mil are pivoted-at ltd and tilt to the fork l and the blade shank llii, respectively, and in is i'ormed. .Due to the relative angularity betweenthe-pivots Mid and tilt in combinationwith the parallelogram motion illustrated, blade shank member tilt may be arly rotated relative to blade fork 62 when cable so is lengthened or be seen that arm lot is pivoted to the fork as at a cooked or skewed angle. It willalsobe seen that when-arm lot is rocked about pivot its the outboard end of am not at pivot its will be moved upand down relative to the planeof the rotor disc. A double pivot arrangement is provided at the outboard end of lever N8 where it connects to link i 09. It will be seen that the pivot at it'll will also move vertically when lever "15 is rocked outboard or inboard. Since link 109 is connected'to lever H0 through a self-aligning bear at pivot it it will cause lever arm H0 compensate tor the normal decreaseintlielenath to tomove the blade shank I or use. result of its iorked pivot arrangement on blade shank fldl at pivot lot. The cable dd is also pivotally connected to the pivot it?! by the clevis lit and the'turnbuckle lid. Lever lid is limited in its outward motion by stop i ll which is adjusted for the highest pitch position of the blade. To the forward end or arm iii is attached a lead weight H2 which may be made up in parts as desired. This weight arm it t is attached to lever lit as though they were a single member so that when lever ,5 ill moves outboard, weight M2 moves inboard. Weight arm ill and its component weights lit are used to obtain a proper balance in the systern. The effective weight of the lever assembly M8, M39 and lid with their bearings, etc., is greater than the momentive efiect of the weight arm lit and weights M2. therefore, when the centriiugal tension increases due to increased rotor speed, the assembly of arms are, it and lid tends to move outboard towardthc stop ill with increasing magnitude according to rotor speed squared.

n the other hancl,the spring M93 is swivelled about the pin Slti which passes through pivot tilt; at one end, and swivels about adjustable'pivot M3 at the other end; thetension in the spring .being adjustable at 566. The spring pivot l 3 is supported by bracket M5 which is fixed to the fork it. It will be seen that the spring ldil augmented by tension in cable it tends to pull the blade into low 'pitch. position and the centrifugal iorce acting on the arms ltd, tilt and H6 tends to cause the blade to go into its high pitch position. in order to equalize the adjustment in the several blades that may comprise a rotor sys= tem, only one of which is shown, the cable 56 is connected to the strap M8 through the adjusting turn-buckle '5 89. Additional tension in cables 8 as mentioned above, is derived from the tension in cable 25 resulting from the action or the cockpit spring at on arms 26 and El and at-,

tachment of Fig. 2.

In Figure 8 there is shown a section taken through the tension-torsion rod assembly of Fig ure 7 lines 8---@ showing the tubular section of tori; 62 and the circumferentially arranged ten-.

sion-torsion rods Figure 9 is an enlarged de-= There are two sources of forces which-tend to keep a blade suspended in a given position. The first is the individual twist or torsion introduced in the tension-torsion rods iii resulting from an tall view or the upper left hand log 52 shown in Figure 6, and a plan view is shown in Figure 10. For each of the tension-torsion rods lid shown in Figure 8 there is provided a pair of lugs hav ing constant thickness and a flat upper surface, as more clearly shown in Figures 9 and 10. Each oi the aforementioned lugs is provided with outwardly opening notches 52a to carry safety re= taining ,wires [12:1 which keep the tension-=torsion rods (it from moving on of lugs 52., The hardened insert'part no is fitted into the irregularly shaped slot 5 5a, in rods at. This insert has a convex sur= face who where it-rests against lugs E52, thus when blade shanlr lot of Figure 6 is rotated relative to the fork 62 the outboard ends of the ten sion-torsion rods are rotated with the blade shank me while theinboard ends of these rods are held stationary since they are attached to fork member 62. It may readily be seen that when this occurs the tension-torsion rods 5d are rotated or rocked on the lugs 52 and the convex surface iof the hardened inserts Hill permit a rocking rather than a sliding motion thereby reducing the friction to a minimum. It may be noted that tension-torsion rods do are cut out with an outwardly tapering clearance in the opening Eda to permit the aforementioned rocking motion with assembly housed in a rairing 622. I

gular displacement of the blade about its longitudinal axis relative to the fork arm 62 in Figure 6, or shank as of Figure 4. This centering force is proportional to the angular displacement of the blade with respect to the hub to which it is linked. The second source of center ing of the blade toward the neutral position is brought about when the tension-torsion rods are skewed away from their normal position (parallel with the axis of the blade or blade shank) while centrifugal tension is acting on the blade. In this case the centrifugal forces tend to straighten out or keep the rods parallel to the center line of the blade shank. Any displacement from the parallel position requires that a torsional force be applied to the blade. rhis force will be proportional to the centrifugal force (R. P. M. squared) and the angular displacement of the blade from its neutral or normal attitude.

In the operation of the jump-take-oii control mechanism the engine 8 is startedin the usual manner by means of its starter 'u'with the rotor clutch 2i disengaged and the handle 26 in its rearward or zero lift position. At the same time, in order that forward motion: is not imparted .to the craftby the tractor propeller Q, the blades of the latter are adjusted by means of the handle 2lla into their sero or lowest pitch position. The rotor system i is then startedby its starter E and its continued rotation is transferred therefrom to the engine 8 by engagementof the clutch l.

the blade pitch control lever 26, the stop having been drawn rcarwardly by the tension spring ill. The rearward movement of the stop 55 from a position forward or" the lever terminal at is permitted due to the correspondingly sloped surfaces Mia and such movement of the stop rearwardly does not interfere either with the released or engaged setting of the clutch lever.

enlarged portion 3% is in engagement with the I tongue Sic due to the end of the slidable plunger 29 having engaged the stop 2% in the rearw rd zero lift position of the handle 2d. Likewise,

when the. hand lever has been moved into its extreme forward or high} pitch. position the transversel slidaol'e plunger 29 is pushed backwardly and rearwardly as a result of its engagement with the stop 32 in which position the re,- duced neck portion 33 of the plunger 29 releases the plunger rod 3! to the influence of the tension spring Bib permitting the tongue 31a; to

latch or loch itself within the notch or. This causes the concurrent forward movement of the levers assess?" is and at which releases the blade pitch in-.- creases tendencies due to slackening of the cable it and increased tension in'the cable til causing the stop le'thereon to be moved forwardly into the dotted position shown in Figure 3. This forward movement of the stop d engages the forked terminal it of the lever 22 causing autosciatic throw-out or release of the clutch it, simultaneously with the increase in lift oi the ill rotor system; The 'power developed by the enone now becomes available for forward thrust and when sumcient altitude has been obted by the lift of the rotor system which rotates for an appreciable period due'to the stored ener y in the form of inertia, the pitch angle of the propeller blades dis increased by operation 5 of the manual control Ella and forward motion of the craft is obtained. The pitch. of the rotor blades can then be manually restored to 1 norrnalsetting by drawing the handle 26 rearwardrotor, the system works asiollowsr With lever M in its rearmost position (blades at zero lift), the rotor blades are set in motion either through power from thecngine 8 drive shaft, etc, or

through an externahsourcc ohpower. It may be noted that the least power is required for turning the blades when they are at their angle of attack of um drag (substantially zero lift); In this attitude with a given source of power the blades may be tumed to their greatest rotational velocity, which may be much greater than the normal s of rotation in flight. The speed of rotation which is greater than normal represents "stored kinetic energy which can he made available for increasing take-oh! performance oi the machine, which is accomplished as follows:

The over center latch sheet of cable it below pivot it when stop it engages stop it holds lever ly until the tongue tic engages in the notchfiil and the other necessary controls are adjusted for the continued flight of the craft. Since the momental weight of the arms wt, ltd, lid, ill, ill and their assembly is greater on the rearward, or side where the arms are disposed, than on the front or leading side where the weight Bill is located, increasing rotor speed causes said arms to exert an increasing eiiort to move out- 243 in its rearmost position, as the speed oi the rotor increases the unbalanced. moment oi the assembly of the control a tilt, the, lit, iii and M2 createsan ihcreasing'unbalanced centriiugal'i'orce acting on said arms which is carried through cable tit and units it, ill; hearing it; case it, and part it to cable Thus when "lever it is pushed forward to the extent that board against the resistance of the spring lit, 5

and the force in the cable til; 'On theother hand, as the rotor speed decreases, the force in the cable t l due to spring t l combined with the momentalforce in the spring ltd about pivot Mi l, including centering efiect oi the. tensiontorsion rods, will become greater than thawsbalanced centrifugal force (as described above) acting on the assembly of control arms ltd, its, lit, ill, M2: Whenthis occurs spring ll operating through cable ill and arm it forces lever 2d backwards from. the high pitch position.

cable it passes smut pivot til, the increased force in cable it will immediately force lever it to its most forward position, shown in dash lines on Figure 2. If a limitation is desired to reduce the rapidity with which the pitch angles are increased, a suitable dash pot or damper cylinder 2%,- may be pivotally connected at ill in his. 2 or may be'inserted where in the eye at which it will retard the i'orwa motion oicabla 2:5. 9 J v Whenthe blades are in their high pitch position the aerodynamic drag on the blades is in- When lever iii reaches the normal pitch position latch pawl tic automatically engages' iotch' so in quadrant t5. 'iihis automatic feature is brought about by the iact that the springs in the system tend to pull the unbalanced weight on the control arms of the blades inboard with a substantially constant force (at any given position of the arms); whereas the centrifugal force acting on the unbalanced moment of said (c) In a design of a power driven rotor it may be iound desirable to have the rotor blades auto matically increase their pitch angle with increascreased and the tendency is to rapidly slow down the rotational speed oi, the rotor. When the speed of the rotor is slowed down, as mentioned above, the force of the sps acting on levers tilt, itll, lid tends to pull them inboard and adjust the pitch to a lower angle of incidence, 7

thus thesystem operates automatically.

It will be seen from the foregoingishat suit able means has been provided for nermitting depending upon the rotorspeed may be utilized:

angular adjustment oi the blades of both the time)? p peller and riltatlngfwing um in relation to the axis of rotation of either with t the development of appreciable friction while the centrifugal forces are acting upon the blades. This has been accomplished by transfer centrifugal tension, in the case of the rotor system, from the blade ill to the fort: arm ti through the plurality of rods Because of the convex surface lite on the insert lit, which his in the slotted portion Etta of the ends oi the rods 66, themotion between each rod and its mating lug 52 as shown in detail in Figs. 9 and 10, is'a rocking motion rather than a sliding motion, and thereiore the only fricnon present is due to rolling friction whic is obviously ezr tremely small. Z111? addition t e mail bearing not mounted internolly at the outboard connection of the rods ht develops an extremely small ins speeds oi the rotor. and conversely to automatlcally decrease their pitch angle with decreasing speed of the rotor. This can be readily accomplished with the present invention.

--"(b) Where it is desired to use the kinetic energy of rotor turning at greater than 'normal speed for increasing thetake-ofr performance of either the power driven or the autorotating type amount of friction only the shear load from theblade ibi tothe forked arm 62. The seli centering sheet which is obtained by this construction also causes rela tively high torsional frequencies oi? the blade and thereby permits successful feather control installations. The foregoing features oi my in-' ventioll are relatively inist in that 9. means the em il; airs I has been found for permitting adjustment of the blade pitch while under centrifugal tension,

but without introducing appreciable friction into the system; and also in that the construction shown for making blade incidence adjustments can be made much lighter than prior arrangements and methods which involve the use of thrust bearings and the like.

Other advantages and modifications of the present invention which may occur to one versed in the art, both in general arrangement and .detail design, are all intended to fall Within the scope and spirit of this invention.

I claim: l

i. In an aircraft sustaining rotor having a hub and an autorotatlve blade, a link member pivotally mounted upon said huh at its inner terminal and having a transversely apertured outer terminal, fork means associated with the said blade pivoted to said outer terminal adapted to permit blade movement within its plane of rotation,

and stop means carried by said linlr outer portion on each side thereof in the path of said blade,

fork adapted normally to limit said blade move ment. about said outer terminal, thesaid stops access-r ment in said parallelogram linkage and relative axial movement of said blade and its support member for blade pitch adjustment.

4. In rotative wine aircraft, a rotatable huh assembly, a rotatable blade system, link means pivotally connecting said blades to the rotatable portion of said halo assembly, hearing means he tween each said blade and itssaid link for pitch adjustment, cable means extending i'rcrn the body of said aircraft to each of said blades for manual pitch adjustment thereof, and cable ecu: pling means disposed within said huh assembly being retractalole'withinsaid link for blade ioldine about said outer, pivot.

2. in rotative wing aircraft, a variable pitch for connecting the rotatable blade portions of said cables to the non-rotatahlemanually onerated control calole portionthe said coupling means comprising an internally splined tubular element fixedto'the aircraft, a terminal for said non-rotatable cable reciprocally engaging said splined portion and having an internal bore, and

. a rotatable terminal element iournalled in an antifriction hearing within said lcore and having said blade cable portions attached thereto.

5. In. rotative wing aircraft, a plurality oi rotatable blades, a huh assembly having a tuhw lar central portion ior the rotational support of said blades, a limit member pivotally carried he said assembly for limited vertical move merit about a horizontal pivot, a blade connect= blade, a support member adapted for the pivotal links and thereby impart rotation to said blade with respect to its co-axial journal upon said support niemloer for control of lolade pitch adiustments. I

3. In ,rotative wing aircraft, a varialile pitch attachment of said blade to the aircraft, bear ins means journalling said blade to said member tor pitch adjustments of the blade with respect to said member about their common axis, a linl; pivoted to said support member on a skewed axis, a second link pivoted to said blade on an axis normal to said blade axis, a third link. pivotallv interconnecting a tree outer terminal, or said.

first two links, said links forming a parallelogram 1 arrangement in which rotationof said first link about its showed axis causes blade pitch rotation with respect to said'support member and cable means connected to one of said outer pivoted connections adapted to impart move log member adapted to interconnect said rnemher with one of said blades, said link them her having a vertical pivot to which the inner end of said connecting member is pivoted for limited movement within its plane of rotation, the said lolade seine co=axiallv iournalled for limited blade pitch adjustment with respect to said connecting member, cahle means for the manualadiustment for the pitch or each of said blades passing through said tuhular huh portion, and a shaft-tor said cahle means pivotally {it} supported upon said huh assembly and rockablv engaging a portion of said linlr member, said shaft rocking in response to pivotal'moven'lents or said linli member with respect to said hub assembly about said horizontal pivot whereby changes in cable tension are automatically corn= blade, a support meniloer adapted for the pivotal j pensatecl for o permit blade pitch-adjustment in all positions of. blade pivotation.

6. In an aircraft sustaining rotor having a hub and an autorotatlve blade, a lint; nieni't r pivotally mounted upon said huh at its inner terminal and having an apertured outer terminal, an arm associated with the said blade pivotallv engaging said outer terminal adapted for hlade pivotati'on in its plane of rotation, and stop means carried on each side of said link outer portion normally disposed in the path or said blade pivotal movement, the said stop means "nee ing manually retractable within said linked por tion for blade folding about said outer pivot.

RICEARD H, Pitts V 173 RC. 

